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<h2><span class="refentrytitle">Struct template when&lt;Grammar, Fun *&gt;</span></h2>
<p>boost::proto::when&lt;Grammar, Fun *&gt; — A specialization that treats function pointer <a class="link" href="../../Transform.html" title="Concept Transform">Transform</a>s as if they
          were function type <a class="link" href="../../Transform.html" title="Concept Transform">Transform</a>s.</p>
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<h2 class="refsynopsisdiv-title">Synopsis</h2>
<div class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../proto/reference.html#header.boost.proto.transform.when_hpp" title="Header &lt;boost/proto/transform/when.hpp&gt;">boost/proto/transform/when.hpp</a>&gt;

</span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Grammar<span class="special">,</span> <span class="keyword">typename</span> Fun<span class="special">&gt;</span> 
<span class="keyword">struct</span> <a class="link" href="when_Gra_1_3_32_5_52_2_1_4.html" title="Struct template when&lt;Grammar, Fun *&gt;">when</a><span class="special">&lt;</span><span class="identifier">Grammar</span><span class="special">,</span> <span class="identifier">Fun</span> <span class="special">*</span><span class="special">&gt;</span> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="when.html" title="Struct template when">proto::when</a>&lt; Grammar, Fun &gt; <span class="special">{</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="id-1.3.32.5.54.7.4"></a><h2>Description</h2>
<p>
            This specialization requires that <code class="computeroutput">Fun</code> is actually a function type.
          </p>
<p>
            This specialization is required for nested transforms such as
            <code class="computeroutput">proto::when&lt;G, T0(T1(_))&gt;</code>. In C++, functions that are used
            as parameters to other functions automatically decay to funtion pointer types. In other words, the
            type <code class="computeroutput">T0(T1(_))</code> is indistinguishable from
            <code class="computeroutput">T0(T1(*)(_))</code>. This specialization is required to handle these
            nested function pointer type transforms properly.
          </p>
</div>
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<div class="copyright-footer">Copyright © 2008 Eric Niebler<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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